The present invention relates to an endlessly circulating items transporting apparatus having a number of transporting members which circulate in a guide, with the transporting members being driven and positioned at the beginning and end of their effective conveying zone by independently controllable drive mechanisms. The apparatus is particularly useful for the transfer of printing products, and a conveying device utilizing such a transporting apparatus is also disclosed.
An items transporting apparatus of this type is disclosed in EP-A-0 309 702 and the corresponding U.S. Pat. No. 4,887,809. This apparatus has an endless guide, on which a number of transporting members are guided in a sliding manner. The transporting members are connected to one another by means of a toothed belt, which is deformed in an undulated form by fastening elements arranged on the transporting members. At the beginning and end of the effective conveying zone there are arranged cam plates, which are each connected to their own drive and the cams of which act on the transporting members in order to drive the latter in the beginning and end region of the effective conveying zone and position them with respect to one another. The spacing of the transporting members outside the effective area of the cam plates is compensated by the resilience of the toothed belt deformed in an undulated manner. Differences in the take-over cycle and delivery cycle or in their phase relationship are offset by increasing or reducing the distance between the transporting members. In the case of this known transporting apparatus, with each cycle the cam plates respectively take along the next-following transporting member in a positionally appropriate manner.
If at the beginning of the effective conveying zone there is no printing product ready to be taken on by a transporting member, the latter continues to run, maintaining the gap in the stream of printing products. Analogously it is not possible with the known transporting apparatus to hold back the delivery of a printing product.
A further similarly acting transporting apparatus is known from Swiss Patent No. 610276 and the corresponding U.S. Pat. No. 4,072,228. Here, the transporting members are connected to one another by means of drag connections and their drive takes place by means of worm wheels which, at the beginning and end of the effective conveying zone, act on follow-up rollers arranged on the transporting members. The driving speed of the first worm wheel is determined by the cycle of a supply conveyor feeding the printing products and that of the second worm wheel is determined by a removal conveyor.
A further transporting apparatus for sheet-like products is disclosed in British Patent No. 966,402. This has a guide which is arranged in a vertical plane, forms a closed loop and along which mutually independent transporting members circulate. Arranged in a region of the guide directed downstream, seen in the circulating direction, is a controllable block which in each case holds back a transporting member until a sheet-like product introduced into the gripper of the transporting member releases the block. Due to gravity, the relevant transporting member then moves with the sheet-like product to the end of the effective conveying zone, where the transporting member is taken up by a transporting chain driven in a circulating manner, in order to be brought along the rising section of the guide at the highest point of the circulating path. At the end of the effective conveying zone, the gripper of the transporting member is opened by means of a link in order to deliver the sheet-like product. It is indeed ensured by this apparatus that each transporting member takes over a sheet-like product at the beginning of the effective conveying zone in order to transport it further. However, a cyclically controlled delivery at the end of the effective conveying zone is not possible.
DE-A-28 22 060 and the corresponding U.S. Pat. No. 4,201,286 further disclose a transporting apparatus with a chain which runs along the guide, is driven in a circulating manner and on to which cyclically controlled transporting members are coupled by means of a transfer wheel at the beginning of the effective conveying zone. The transfer wheel is driven in time with a supply conveyor, which delivers printing products in imbricated formation and introduces them into the opened gripper of the transporting member taken up by the transfer wheel. Arranged at the end of the effective conveying zone is a cam wheel, which is coupled to a removal conveyor and in each case takes along a transporting member in order to transfer the printing product to a gripper of the removal conveyor. The mutually independent transporting members are designed in such a way that the coupling to the drive chain is released as soon as transporting members run one onto the other. The transfer wheel is preceded by a controllable blocking element, which holds back over one cycle that transporting member to which a missing printing product in the imbricated formation would be allocated. As a result, no empty grippers can be taken up by the transfer means and further conveyed. A similar blocking element precedes the cam wheel, in order to interrupt temporarily the delivery of printing products to the removal conveyor. This known transporting apparatus is complex in construction and is suitable only for substantially rectilinear conveying zones.